1.
Two species of wild lettuce grow in the same areas, but one flowers in early spring and the other flowers in summer. This is an example of a:
Correct Answer
A. Temporal isolating mechanism
Explanation
This scenario describes a temporal isolating mechanism, where the two species of wild lettuce have different flowering times. This prevents them from interbreeding because they are not in reproductive synchrony. This temporal isolation helps maintain the genetic integrity of each species by reducing the chances of hybridization and gene flow between them.
2.
The sperm of species A dies when it comes in contact with the female reproductive tract of species B. This is an example of:
Correct Answer
A. A prezygotic isolating mechanism
Explanation
The given scenario describes a situation where the sperm of species A is unable to successfully fertilize the eggs of species B due to death upon contact with the female reproductive tract. This is an example of a prezygotic isolating mechanism, which refers to barriers that prevent the formation of a zygote (fertilized egg) between different species. In this case, the reproductive barrier occurs before fertilization can even take place, as the sperm dies upon contact. This mechanism helps to maintain reproductive isolation between species by preventing the formation of viable offspring.
3.
Which of these isolating mechanisms occurs at the pre-mating stage?
Correct Answer
A. GeograpHic isolation
Explanation
Geographic isolation is an isolating mechanism that occurs at the pre-mating stage. It refers to the physical separation of populations by geographical barriers, such as mountains, rivers, or oceans. This separation prevents individuals from different populations from coming into contact and mating with each other, leading to reproductive isolation. Over time, genetic differences can accumulate between the isolated populations, eventually resulting in the formation of new species. Therefore, geographic isolation plays a crucial role in speciation by preventing gene flow between populations.
4.
Which of the following statements is NOT true about natural selection?
Correct Answer
A. Natural selection directs the course of evolution by preserving traits acquired during an individual’s lifetime
5.
Random evolutionary changes in a small breeding population is known as:
Correct Answer
B. Genetic drift
Explanation
Genetic drift refers to the random changes in the frequency of certain traits within a small breeding population. It occurs due to chance events, such as the death or reproduction of individuals, rather than natural selection. Unlike natural selection, genetic drift does not necessarily lead to adaptations that improve the population's fitness. Instead, it can result in the loss or fixation of certain traits over generations.
6.
Seriously abnormal phenotypes or harmful mutations are acted against or reduced to low frequencies by:
Correct Answer
E. Natural selection
Explanation
Natural selection is the process by which organisms with traits that are advantageous for their environment are more likely to survive and reproduce, passing on those traits to future generations. In the case of seriously abnormal phenotypes or harmful mutations, individuals with these traits are less likely to survive and reproduce, resulting in a reduction of these traits in the population over time. Therefore, natural selection acts against or reduces the frequency of seriously abnormal phenotypes or harmful mutations.
7.
The migration of breeding individuals between populations causes a corresponding movement of alleles, which is referred to as:
Correct Answer
D. Gene flow
Explanation
Gene flow refers to the movement of alleles between populations through the migration of breeding individuals. This movement of alleles can result in the mixing of genetic material and can have significant effects on the genetic diversity and composition of populations. Gene flow can introduce new alleles into a population, increase genetic diversity, and counteract the effects of genetic drift or natural selection. Therefore, gene flow is the correct answer in this context.
8.
Because of fluctuations in the environment a population may periodically experience a rapid decrease in the number of individuals. When this occurs, genetic drift can occur in the few remaining survivors, a process referred to as:
Correct Answer
C. A genetic bottleneck
Explanation
A genetic bottleneck refers to a situation where a population undergoes a significant reduction in size, resulting in a limited number of individuals surviving. This reduction in population size can lead to genetic drift, where the frequency of certain alleles can change due to chance events. The surviving individuals may not represent the full genetic diversity of the original population, leading to potential changes in the genetic makeup of the population over time.
9.
The process that decreases the number of organisms with phenotypes less fit to meet environmental challenges is:
Correct Answer
A. Natural selection
Explanation
Natural selection is the process that decreases the number of organisms with phenotypes less fit to meet environmental challenges. It is a fundamental mechanism of evolution where individuals with advantageous traits are more likely to survive and reproduce, passing on their genes to the next generation. Over time, this leads to the accumulation of beneficial traits in a population, increasing its overall fitness and adaptation to the environment. Genetic drift, gene flow, genetic polymorphism, and migration may also play a role in shaping populations, but they do not specifically target and decrease the number of organisms with less fit phenotypes.
10.
When phenotypes are favoured at one extreme of a normal distribution, selection occurs:
Correct Answer
B. Directional
Explanation
When phenotypes are favored at one extreme of a normal distribution, selection occurs in a directional manner. This means that individuals with traits closer to that extreme will have higher fitness and therefore higher chances of survival and reproduction. Over time, this will cause the average phenotype of the population to shift towards that extreme. Stabilizing selection, on the other hand, favors the intermediate phenotypes, while disruptive selection favors the extremes. Frequency-dependent selection occurs when the fitness of a phenotype depends on its frequency in the population. The term "abnormal" is not applicable to this context.
11.
Frequency dependent selection acts to decrease the frequency of which phenotype in a population?
Correct Answer
D. The most common pHenotype
Explanation
Frequency dependent selection acts to decrease the frequency of the most common phenotype in a population. This is because when a phenotype becomes more common, it becomes more easily targeted by predators or competitors, reducing its fitness. As a result, individuals with less common phenotypes have a higher fitness advantage, leading to a decrease in the frequency of the most common phenotype over time.
12.
In selection, individuals with a phenotype near the mean are favoured over those with phenotypic extremes
Correct Answer
C. Stabilizing
Explanation
In stabilizing selection, individuals with a phenotype near the mean are favored over those with phenotypic extremes. This means that individuals with average or intermediate traits have a higher chance of survival and reproductive success compared to those with extreme traits. This type of selection tends to maintain the existing phenotypic variation within a population and reduces the occurrence of extreme traits.
13.
Human birth weight is a good example of:
Correct Answer
E. Stabilizing selection
Explanation
Stabilizing selection refers to a type of natural selection where the extreme variations of a trait are selected against, and the average or intermediate variations are favored. In the case of human birth weight, stabilizing selection would mean that babies with extremely low or high birth weights are less likely to survive or have a higher risk of health complications, while babies with average birth weights have better chances of survival and are more likely to be healthy. This leads to a stabilizing effect on birth weight, with most babies being born within a certain range of weights.
14.
The prevention of genetic exchange between two species because they reproduce at different times of the day, season or year is called:
Correct Answer
E. Temporal isolation
Explanation
Temporal isolation refers to the prevention of genetic exchange between two species because they reproduce at different times of the day, season, or year. This means that individuals from different species are unable to mate and produce offspring because their reproductive cycles do not align. This type of isolation plays a crucial role in speciation, as it leads to the accumulation of genetic differences between populations over time.
15.
The distinctive mating signals that have evolved as part of animals courtship illustrates what type of reproductive isolating mechanism?
Correct Answer
A. Behavioral isolation
Explanation
Behavioral isolation is a type of reproductive isolating mechanism where individuals of the same species have different courtship behaviors or mating signals. This prevents individuals from different species from successfully mating and producing viable offspring. In this case, the distinctive mating signals that have evolved as part of animals' courtship indicate that behavioral isolation is the correct answer.
16.
When the reproductive cells of different species are incompatible, it is referred to as:
Correct Answer
B. Gametic isolation
Explanation
Gametic isolation refers to the incompatibility of reproductive cells between different species. This means that the sperm of one species is unable to fertilize the egg of another species, or if fertilization occurs, it does not result in viable offspring. This can be due to differences in the structure or composition of the gametes, preventing successful fertilization. This type of isolation plays a role in preventing gene flow between species and maintaining reproductive barriers.
17.
The geographic isolation of Kaibab squirrels from Albert squirrels appears to be leading to:
Correct Answer
D. Allopatric speciation
Explanation
Allopatric speciation is the process by which new species arise due to geographic isolation. In this case, the geographic isolation of Kaibab squirrels from Albert squirrels is leading to allopatric speciation. This means that the two populations of squirrels are separated by a physical barrier, such as a mountain range or body of water, preventing them from interbreeding. Over time, this isolation can lead to the accumulation of genetic differences between the two populations, eventually resulting in the formation of distinct species.
18.
If two species are able to interbreed but produced sterile hybrids, their species integrity is maintained by:
Correct Answer
D. A postzygotic barrier
Explanation
A postzygotic barrier refers to a reproductive barrier that occurs after the formation of a hybrid zygote. In this scenario, two species are able to interbreed, but the hybrids they produce are sterile. This means that the hybrids are unable to produce viable offspring, thus maintaining the species integrity. This postzygotic barrier prevents gene flow between the two species, as the sterile hybrids are unable to pass on their genes to the next generation.
19.
Cattle breeders have improved the quality of meat over the years by which process?
Correct Answer
D. Artificial and directional selection only
Explanation
Cattle breeders have improved the quality of meat over the years through artificial and directional selection. Artificial selection involves selecting and breeding animals with desired traits, such as higher meat quality, to pass those traits on to future generations. Directional selection occurs when breeders select for extreme variations of a trait, such as larger size or higher meat yield, further enhancing the desired qualities in the population. Stabilizing selection, on the other hand, maintains the average traits in a population and does not contribute to the improvement of meat quality in this context.
20.
Which of the following is NOT considered a reproductive isolating mechanism?
Correct Answer
C. Feeding behaviour
Explanation
Feeding behavior is not considered a reproductive isolating mechanism because it does not directly prevent individuals from successfully reproducing with each other. Reproductive isolating mechanisms are barriers that prevent individuals from different species or populations from interbreeding, such as ecological isolation, gametic incompatibility, and timing of courtship display. Sterile offspring is also a reproductive isolating mechanism as it prevents successful reproduction. However, feeding behavior does not directly impact the ability to reproduce and therefore is not considered a reproductive isolating mechanism.
21.
Which of the following reproductive isolating mechanisms is postzygotic?
Correct Answer
C. Hybrid sterility
Explanation
Hybrid sterility is a postzygotic reproductive isolating mechanism, meaning it occurs after the formation of a hybrid offspring. In this case, the hybrid offspring is unable to reproduce or produce viable offspring, leading to reproductive isolation between the two parent species. This mechanism prevents gene flow and maintains the genetic integrity of the parent species. In contrast, prezygotic mechanisms such as habitat isolation, temporal isolation, behavioural isolation, and gamete incompatibility occur before the formation of a hybrid offspring.
22.
Although different species of warblers often migrate together and use the same habitats for mating and feeding, they rarely hybridize. The isolating mechanism, most likely to be operating is:
Correct Answer
C. Behavioural isolation
Explanation
Behavioural isolation is the most likely isolating mechanism operating in this scenario. This is because despite different species of warblers migrating and using the same habitats, they rarely hybridize. This suggests that there are behavioral differences between the species that prevent them from mating with each other. These behavioral differences could include differences in courtship rituals, mating calls, or other behaviors that are specific to each species. These behavioral barriers prevent interbreeding and maintain reproductive isolation between the warbler species.
23.
Some species of Anopheles mosquito live in brackish water, some in running freshwater, and others in stagnant water. What type of reproductive barrier is most obviously separating these different species?
Correct Answer
A. Ecological isolation
Explanation
Ecological isolation is the most obvious reproductive barrier separating different species of Anopheles mosquitoes. This is because these mosquitoes live in different types of water habitats, such as brackish water, running freshwater, and stagnant water. The different species of mosquitoes are adapted to their specific ecological niches and do not come into contact with each other due to their habitat preferences. This prevents them from interbreeding and maintaining reproductive isolation.
24.
The reproductive barrier that maintains the species boundary between horses and donkeys is:
Correct Answer
D. Hybrid sterility
Explanation
Hybrid sterility is the correct answer because it refers to the inability of the offspring produced from the mating of horses and donkeys to reproduce. This reproductive barrier prevents gene flow between the two species and maintains their species boundary. While mechanical isolation refers to physical differences that prevent mating, gametic isolation refers to the inability of sperm and eggs to fertilize, hybrid in-viability refers to the offspring being unable to survive, and hybrid breakdown refers to the reduced fitness or viability of subsequent generations of hybrids.
25.
Review the image and answer the following question.The tendency for human infants to weigh 7 lbs at birth is an example of what kind of selection?
Correct Answer
B. Stabilizing selection
Explanation
Stabilizing selection refers to a type of natural selection where individuals with intermediate traits are favored, while extreme traits are selected against. In the case of human infants weighing around 7 lbs at birth, this is an example of stabilizing selection because babies with weights significantly lower or higher than 7 lbs are more likely to face health complications. Therefore, the selection pressure favors infants with an average weight, leading to a stable distribution of birth weights around 7 lbs.